Electric field sensors are useful for measuring electric field strengths in a variety of contexts. One such context is the downhole environment. In downhole applications, electric field sensors are often used to measure close-proximity electric fields that reflect material properties of the surrounding formation—for example, the depth, thickness, and lateral extent of ore bodies, hydrocarbons, water, and environmental pollutants. Characterizing such material properties is of significant value in terms of maximizing hydrocarbon yield and operational efficiency and minimizing losses due to equipment and environmental damage. Existing techniques for measuring such electric fields, however, are insufficiently insensitive.
For instance, in some enhanced oil recovery efforts, water is injected into a dead well to increase hydrocarbon throughput in an adjacent, producing well. The injected water approaches the producing well in what is called a “water flood,” If the water flood crosses a threshold distance from the producing well, the fluid produced by the producing well may become contaminated with the water. Existing techniques for measuring electric fields often fail to detect such water floods until they are too close to the producing well and have already begun to dilute the hydrocarbons that the well produces, resulting in significant financial losses. Similarly, existing electric field sensors are often too insensitive to detect hydrocarbons that are available for extraction from the formation, resulting in substantial opportunity costs. A highly sensitive electric field sensor, therefore, is desirable.
It should be understood, however, that the specific embodiments given in the drawings and detailed description thereto do not limit the disclosure. On the contrary, they provide the foundation for one of ordinary skill to discern the alternative forms, equivalents, and modifications that are encompassed together with one or more of the given embodiments in the scope of the appended claims.